又有野唔識做啦.....急急急!!

Q2...7 (3-X)+3(2-X) = (6-X) - (3-7X) +18
21 - 7x + 6 - 3x = 6 - x - 3 + 7x + 18
-16x = -6
x = 3/8

Q3...8(2X-2) +4(X+1)=3(X15)
你條式有問題 , 3(X+15) 定係 3(X-15)？

Q4... 2m-3 (4-m)=2(m+1)=7
你條式又有問題 , 唔該你睇清楚邊個係 = , 邊個係+？

Q5...-1.5 (1.5-X)+0.2(0.5X+1.25)=0.6X-6

-2.25+1.5x+0.1x+0.25 = 0.6x-6
x = -4

Q1.Let the price of the model be x,and the save of Bobby each day be y
5y+70=x
9y+10=x
so 5y+70=9y+10
5y+70=9y+10
4y=60
y=15
so Bobby save 15$ each day

Q2 7 (3-X)+3(2-X) = (6-X) - (3-7X) +18
21-7x+6-3x = 6-x-3+7x+18
12 =16x
x = 12/16

Q3 不明白你這式中的3(x15) ,所以我當作3(x-15)
8(2X-2) +4(X+1)=3(X15)
16x-16+4x+4=3x-45
33=-17x
x=33/-17

Q4 又不知你為何加多了一個=7在最後所以我當作-7
2m-3 (4-m)=2(m+1)=7
2m-12+3m=2m+2-7
-m=7
m=-7

Q5 -1.5 (1.5-X)+0.2(0.5X+1.25)=0.6X-6
-2.25+1.5x+0.1x+0.25=0.6x-6
x=8

希望幫到你啦^^

1. Let x be his saving
5x + 70 = 9x + 10
60 = 4x
x = 15

2. 7 (3-X)+3(2-X) = (6-X) - (3-7X) +18
21 - 7x + 6 - 3x = 6 - x - 3 + 7x + 18
6 = 16x
x = 3/8

3. 條問題最尾打錯....

4. 呢條都好似打錯....有兩個 "="....

5. -1.5 (1.5-X)+0.2(0.5X+1.25)=0.6X-6
-2.25 + 1.5x + 0.1x + 0.25 = 0.6x - 6
4 = -x
x = -4